Redundant system and load drive control device

Provided is a redundant system capable of executing a start request received during update of a microcomputer control program even when an external nonvolatile memory is employed in a redundant system in which one load is controlled by a plurality of control circuits having a redundant configuration, the redundant system being low in cost and excellent in responsiveness. In the redundant system that controls one load by a plurality of control systems having a redundant configuration, when an update program signal for the plurality of control systems is received, update of a control program for each of the plurality of control systems in a predetermined order is individually executed, and when a start request of the load is received during the execution of the update of a control program of one predetermined system, the load is controlled by a system other than the one predetermined system, and during the control, the update of the control program of the one predetermined system is continued.